Inhibition of corrosion and hydrogen embrittlement of a HSLA steel in 0.5 M H2SO4 by nitrile compounds

The inhibitive action of valeronitrile, benzonitrile and derivatives of benzonitrile on the corrosion and hydrogen embrittlement behaviour of HSLA steel in 0.5 M H2SO4 was investigated. All these inhibitors reduced the corrosion rate of the steel with naphthonitrile showing the highest inhibitive efficiency and valeronitrile the lowest. All the inhibitors adsorbed on the steel as per the Temkin adsorption isotherm. The steel become less active on the addition of benzonitrile, 3-chlorobenzonitrile, 4-chlorobenzonitrile, 4-methylbenzonitrile and naphthonitrile to the acid while valeronitrile and 2-chlorobenzonitrile made the steel more active. Naphthonitrile reduced the rate of the hydrogen evolution reaction most efficiently. Derivatives of benzonitrile inhibited hydrogen absorption most effectively.